Maths GCSE Higher Tier Edexcel Notes
Chapter 1 - Chapter
- Created by: Annie
- Created on: 09-10-10 09:45
Notes One Chapter One Numbers - Dividing By
Dividing By Decimals
- Rewrite division as fraction.
- Mulitply top and bottom of fraction by a number that makes both division numbers whole numbers.
- Work out anwer (use long division if nessecary.)
Example
- 240 divived by 0.06
- 240 over 0.06
- 240 over 0.06 times 100.
- 24000 over 6
- Equals 4000.
Notes One Chapter One Numbers - Rounding To
Rounding To Significant Figures
- The first sigificant figure is the first non-zero digit when reading left to right.
3.46 or 0.00000345
- The second sigificant figure is the digit directlty after the first sigificant figure, this can be zero.
3.46 or 0.00000345
- If your asked to round to round to a certain sigificant figure then you find the sigificant figure first then round the number to this accuracy.
34061 (2 sigificant figures) = 34000
Notes One Chapter One Numbers - Estimating
Estmating
In maths (non-calctuator exam) estimating means something very specific.
- Round each of the separate numbers in the sum to a nice easy number (1 s.f).
- Do calculation in head with these easy numbers.
- Show every step of your workings.
Notes One Chapter One Numbers - Square Roots
Square Roots and Cube Roots Of Decimals
Square numbers are:
1, 4, 9, 16, 25, 36, 49, 64, 81, 100, 121, 144, 169, 196, 225, 289, 324, 361, 400.
Cube numbers are:
1, 8, 27, 64, 125, 216, 343, 512, 729, 1000.
Square roots always have two possible answers. For example 16 square rooted is 4 and -4.
Cube roots only have one answer and it's always the same sign as the question.
Notes One Chapter One Numbers - Factors
Factors
A factor is a number that goes into another number without a reminder.
6 is a factor of 64 because 6 x 9 = 54.
A prime number has only two factors.
6 is not a prime factor as it has 4 factors = 1, 6, 2, 3
1 is not a prime number as it has only 1 factor = 1
17 is a prime factor as it has 2 factors = 1, 17
This is a factor which is also a prime number:
18 has factors = 1, 18, 2, 9, 3, 6
18 has prime factors = 2, 3
Notes One Chapter One Numbers - Highest Commo
Highest Common Factor is the largest number which is a factor of two or more numbers.
For example: What is the highest common factor of 18 and 24?
Factors of 18 = 1, 18, 9, 2, 3, 6.
Factors of 24 = 1, 24, 2, 12, 3, 8, 4, 6.
Common factors of 18 and 24 = 1 and 2.
Therefore highest common factor of 18 and 24 is 2!
Notes One Chapter One Numbers - Mutiples
A mutiple of a number is a number that is divisable by the starting number (ie the times table.)
For example :
Mutliples of 14 = 14, 28, 42, 56, 70 etc.
Mutliples of 5 = 5, 10, 15, 20, 25, 30 etc.
Notes One Chapter One Numbers - Lowest Commo
A lowest common multiple is the smallest number in which a number appear in the list of mulitples of every number concerned.
For example:
What is the lowest common multiple of 14 and 21?
Mutliples of 14 = 14, 28, 42, 56, 70, 84 etc.
Multiples of 21 = 21, 42, 63, 84, 105 etc.
The lowest common multiple of 14 and 21 = 42, 84.
The answer is 42 as they is the smallest number.
Notes One Chapter One Numbers - Factor Trees.
These are used for questions which ask you to find:
- Product of prime factors.
- Highest common factor.
- Lowest common mulitple.
Method:
- Start by writing the number at the top centre of the page.
- Split the number into a factor pair, branching of below.
- Ring any factor that appears that is a prime number.
- Repeat process untill every branch ends in a prime number.
Notes One Chapter One Numbers - Expressing A
Product means you mulitply.
You need to use factor tree to find prime factors. You then write out prime factors in oder with a mulitplier between each one. Then you just simplify to index notation.
For example:
Express 98 as a product of its primes.
98 = 2 times 7 times 7.
98 = 2 times 7 to the power of 2.
Notes One Chapter One Numbers - Finding All
It is possible to find all of the prime factors by mulitpling some the of prime factors together.
For example:
Factors of 24 = 1, 24, 2, 12, 3, 8, 4, 6.
24 has prime factors = 2, 2, 2, 3.
We got the three 2s from the factor 4 and factor 2, we got 3 from the factor 3.
Notes One Chapter One Numbers - Highest Commo
Method:
- Find each number as a product of its primes.
- Write these products one under the other so that the same bases line up.
- If one of the product of prime factors is missing add a column add it to the power of zero.
- Looking down each column choose the base with the smallest power.
- Times the products of prime with the smallest power to together to get to highest common factor.
Notes One Chapter One Numbers - Lowest Common
Lowest common factor is the same as highest common factor but this time you choose highest powers!
So....
- Find each number as a product of its primes.
- Write these products one under the other so that the same bases line up.
- If one of the product of prime factors is missing add a column add it to the power of zero.
- Looking down each column choose the base with the highest power.
- Times the products of prime with the highest power to together to get to highest common factor.
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